Timing arrangement



a. F. LEWIS 2,317,783

TIMING ARRANGEMENT April 27, 1943.

Filed May 14, 1941 lNl/ENTOR B. E LEW/5 A TTO/PNEV Patented Apr. 27,1943 UNITED STATES PATENT OFFICE Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application May 14, 1941,Serial No. 393,389

4 Claims.

This invention relates to timing means for use in telephone systems andhas for its object the provision of a timing device requiring no specialmachines or sources of current supply.

In automatic telephone systems, if the operations do not proceedsmoothly, some means must be provided to dispose of uncompleted calls,for example, by signaling an attendant. For this purpose the variouspieces of equipment have associated with them some form of signalingmeans which is operated under the control of common timing means. Inlarge oifices this timing means may be a mechanical interrupter.

While it has heretofore been suggested that some form of electricalinterrupter be employed using gas-filled tubes, such arrangementsusually required a source of high potential and in some ofiices no suchsource. is available.

In accordance with the present invention, a timing arrangement isprovided in which rectified alternating current obtained from a constantvoltage rectifying device is used to charge a condenser, which suppliesthe breakdown potential to a gas-filled tube.

More specifically, a single tube acts both as the voltage across thecondenser at the end of the timing period. In this arrangement thetiming condenser l is biased by a battery of -48 volts. The tube 2 is ofthe type having a high anode-cathode breakdown voltage and a lowdeionization time. The first characteristic allows the use of asufiiciently high alternating current potential on the anode to operatethe relay, Without the occurrence of anode breakdown independent of thecontrol electrode. The second characteristic allows the use of analternating current potential on the anode of the commercial frequencyof 60 cycles.

Alternating current voltage from source 3 is applied through transformer4 to the anode 5 and the cathode 6 of the tube 2. The arrangement issuch that the anode supply El may be 80 to 200 volts and the cathodebias E2 may be 55 to 80 volts. Relay 1 is a slow-release relay whichoperates from the pulsating current that flows when the anode-cathodegap breaks down.

Ill

Ill

With switch 8 in its lower position on contact 9, condenser l dischargesthrough resistance l0 and tube 2 is extinguished, since the deionizationtime of the tube is less than a half cycle of source 3 and the anodecurrent ceases when the voltage from anode 5 to cathode 6 becomesnegative. With tube 2 extinguished, relay 1 releases. The timed periodis started by moving switch 8 to its upper position onto contact ll. Thesubsequent action of the circuit depends on the value of voltage El, themore stable action occurring when El is between 80 and 115 volts.

Assume that El is 100 volts and that E2 is 60 volts. Under thisassumption, at the start of the timed period, during the half cycleswhen voltage El is positive to ground and E2 is negative to ground, nocurrent can flow because the potential between the control anode l2 andthe cathode 6 is always less than the breakdown value for this gap. Thebreakdown voltage is 65-75 volts, while the applied potential variesfrom 48 volts to +37 volts. Similarly no current can flow from anode 5to the control anode l2 or to the cathode 6 because the potential acrossthese gaps, which varies from 0 to 225 volts, is always less than thebreakdown voltage of these gaps.

During the half cycles when El is negative to ground and E2 is positive,the potential across the control gap varies from 48 to 133 volts andfrom the time that it equals the breakdown value of the control gap tothe time that it becomes less than the sustaining values, that is 55-65volts, a charging current flows to the condenser from ground, throughthe winding of transformer 4, winding of relay 1, from cathode B tocontrol anode l2 through the tube 2, resistance l3, switch 8 tocondenser I. As a result, the charge on condenser l increases and thepotential on the tube side of the condenser l becomes more positive.

When the charge on condenser l becomes sufliciently positive, thepotential between control anode l2 and cathode 6, during a half cyclewhen El is positive to ground and E2 is negative, equals or exceeds thebreakdown value of the control gap for a sufficient length of time forthe ionization of the control gap to cause the main gap, between anode 5and cathode 6 to also break down.

During the following half cycle, the charging current again flows. Theamount of this charging current on the succeeding half cycles when El isnegative to ground, diminishes until it is only sufiicient to restorethe condenser charge that is dissipated by the ionization of the controlpath during the half cycles when El is positive to ground. No currentflows at this time between anode 5 and cathode 6 since the voltage isnot sufficient to break down this gap in the reverse direction eventhough the control gap is ionized.

During successive half cycles when El is positive, the gap between anode5 and cathode 6 is repeatedly broken down in the manner above described.Relay operates in response to the pulses of current which flow duringthese half cycles and, due toits slow-releasing character, holds closedthe circuit controlled by it.

Relay 1 is released by moving switch 8 to its lower position. Whileshown as a manual switch, switch 8 would probably be a relay contact,closed to the upper position when it is desired that the timing startand closed to its lower position when the timing has been completed oris no longer needed.

For higher values of El reverse breakdown takes place between controlanode l2 and anode 5 and also between cathode 6 and anode 5 during thehalf cycles when El is negative resulting in a slower charging rate forcondenser I.

With this circuit the timed period may be varied from .25 second to 10seconds. The time limits are determined by resistance I3, the minimumtime being determined by the value of resistance [3 which will limit thecurrent from the cathode 6 to the control anode 12 to a safe value forthe tube, while the maximum time depends on the value of resistance l3which will provide a sufficiently large ionizing current from thecontrol anode l2 to the cathode 6 to cause ionization of theanode-cathode gap when E! is positive to ground.

What is claimed is:

1. A timing device comprising a gas-filled tube having an anode, acathode and a control anode, a source of alternating voltage, means toconnect said source with said tube so that the potentials simultaneouslyapplied to said anode and said cathode vary reversely, a condenserconnected in series with said control anode cathode path, responsivemeans connected in series with said cathodeanode path, means to applyincrements of charge to said condenser during half cycles when saidcathode is positive, said responsive means operating during a half cyclewhen said anode is positive in response to a charge on said condensersufiicient to render the anodecathode path conducting.

2. A time delay device comprising a gas-filled tube having a control gapand a main gap, a condenser, a resistance, a source of alternatingcurrent and a load device, means for deriving a pair of reciprocallyvarying sources of alternating voltage from said current source, andcircuits connecting one of said voltage sources with said condenser andresistance in series with said control gap and connecting the other ofsaid sources of voltage with said load device in series with said maingap, said tube acting as a rectifier for charging said condenser and asa detector to operate said load device responsive to a predeterminedcharge on said condenser.

3. A time delay device comprising a gas-filled tube having an anode, acathode and a control anode, a source of alternating current, means toconnect said source with said cathode and anode so that potentialssimultaneously applied thereto are of opposite polarity, a load devicein said cathode-anode circuit, a condenser, a resistance and a battery,means to connect said condenser, said resistance and said battery inseries with the cathode-control anode circuit of said tube, saidcondenser receiving increments of charge on alternate half cycles ofsaid source until the breakdown potential from said control anode tosaid cathode is reached, said cathode-anode circuit becoming conductingresponsive to said breakdown potential to operate said load device.

4. A time delay device comprising a gas-filled tube having an anode, acathode and a control anode, a source of alternating current, means toconnect said source with said cathode and anode so that potentialssimultaneously applied thereto are of opposite polarity, a load devicein said cathode-anode circuit, a condenser, a resistance and a battery,means to connect said condenser, said resistance and said battery inseries with the cathode-control anode circuit of said tube, saidcondenser receiving increments of charge on alternate half cycles ofsaid source until the breakdown potential from said control anode tosaid cathode is reached, said cathode-anode circuit becoming conductingresponsive to said breakdown potential to operate said load device, saidcharging circuit and said cathode-anode circuit being subsequentlyeffective in response to successive half cycles of said source, andmeans ,to hold said load device operated during the half cycles whensaid charging circuit is efiective.

BENJAMIN LEWIS.

